rate of chemical reactions

[thisongaintgottaname]

Which of the following changes will Always ensure an increase in the rate of a chemical reaction?
I adding a catalist
II Increasing temp
III Increasing conc
IV Increasing the surface area of the reactant

A I only
B I,II and III only
C I, II, and IV only
D I, II, III and IV

answer says B. It excludes option IV, which looks fine to me?
Have i overlooked anything?

[kendraaaaa]

What if the reactant's a gas? Not sure if that's correct but that was my thinking when doing this question

[Edmund]

I've seen this question somewhere before.

This is what I think. Increasing surface area increases the frequency of collisions, but it is only the frequency of successful collisions that accounts for increased rate of reaction. So increasing the surface area itself doesn't increase rate, and probably the other 3 factors does this...

[sachinmachin]

I've seen this question somewhere before.

This is what I think. Increasing surface area increases the frequency of collisions, but it is only the frequency of successful collisions that accounts for increased rate of reaction. So increasing the surface area itself doesn't increase rate, and probably the other 3 factors does this...

+1

[NE2000]

I've seen this question somewhere before.

This is what I think. Increasing surface area increases the frequency of collisions, but it is only the frequency of successful collisions that accounts for increased rate of reaction. So increasing the surface area itself doesn't increase rate, and probably the other 3 factors does this...

Increasing concentration does precisely the same thing. Only a catalyst and temperature affects the overall proportion of particles that have sufficient activation energy (looking at Maxwell-Boltzman curves). To increase rate of reaction it is often sufficient to increase frequency of collisions, as for a given number of collisions there will always be a certain percentage particles with sufficient energy for reaction. Increasing the surface area does increase rate.

The crux of the question may indeed be the always, it would seem somewhat obvious that when speaking of surface area you refer to a solid, but the answers may be driven by the idea that for a gas 'surface area' will not make a difference.

[thisongaintgottaname]

I've seen this question somewhere before.

This is what I think. Increasing surface area increases the frequency of collisions, but it is only the frequency of successful collisions that accounts for increased rate of reaction. So increasing the surface area itself doesn't increase rate, and probably the other 3 factors does this...

Increasing concentration does precisely the same thing. Only a catalyst and temperature affects the overall proportion of particles that have sufficient activation energy (looking at Maxwell-Boltzman curves). To increase rate of reaction it is often sufficient to increase frequency of collisions, as for a given number of collisions there will always be a certain percentage particles with sufficient energy for reaction. Increasing the surface area does increase rate.

The crux of the question may indeed be the always, it would seem somewhat obvious that when speaking of surface area you refer to a solid, but the answers may be driven by the idea that for a gas 'surface area' will not make a difference.

THANK YOU GUYS

[bloodboy]

Is this from chemology 09? If so, I think you've left out some pretty important details in the question

[Over9000]

I've seen this question somewhere before.

This is what I think. Increasing surface area increases the frequency of collisions, but it is only the frequency of successful collisions that accounts for increased rate of reaction. So increasing the surface area itself doesn't increase rate, and probably the other 3 factors does this...

Increasing concentration does precisely the same thing. Only a catalyst and temperature affects the overall proportion of particles that have sufficient activation energy (looking at Maxwell-Boltzman curves). To increase rate of reaction it is often sufficient to increase frequency of collisions, as for a given number of collisions there will always be a certain percentage particles with sufficient energy for reaction. Increasing the surface area does increase rate.

The crux of the question may indeed be the always, it would seem somewhat obvious that when speaking of surface area you refer to a solid, but the answers may be driven by the idea that for a gas 'surface area' will not make a difference.

Crux AND indeed, ur on a roll.

[kendraaaaa]

by the way, can you pls upload chemology 09 by any chance?

+1

[StringFever]

by the way, can you pls upload chemology 09 by any chance?

+1

+1